JP5495027B2 - Wheel braking force estimation device and vehicle motion control device equipped with the device - Google Patents

Description

  The present invention relates to a wheel braking force estimation device, and more particularly to a device for calculating a braking force generated by each wheel and a vehicle motion control device using this device.

  In Patent Document 1, a braking force applied to each wheel of a vehicle is estimated, a difference in braking force applied to the left and right wheels is estimated based on the estimated braking force, and according to the left and right braking force difference. Further, it is described that assist steering torque is applied to assist an operation during counter-steering.

  In Patent Document 2, the sum of lateral forces Fya # acting on the left and right wheels, the balance equation of forces in the lateral direction of the vehicle, and the yaw moment Mfx resulting from the left / right difference in wheel braking force (front / rear force) are described. It is described that calculation is performed based on the lateral acceleration Gy and the time differential value dYr of the yaw rate, and the vehicle stabilization control is performed based on the sum Fya # of the lateral forces using the rotational motion equation for the vehicle yaw motion including Has been.

  In the vehicle motion control apparatus as described in Patent Document 1 and Patent Document 2 described above, it is necessary to estimate the braking force acting on the wheels.

  Patent Document 3 describes that the wheel cylinder pressure of each wheel is estimated based on the measurement result of a pressure sensor attached to the master cylinder pressure. Specifically, it is described that the wheel cylinder pressure of each wheel is obtained from the measured supply pressure (master cylinder pressure) and valve operation time.

JP 2003-291838 A JP 2009-241721 A JP-A-7-186918

  In the friction brake device, a braking force is generated on the wheel by the frictional force of a friction member (such as a brake pad). Since the friction coefficient of the friction member changes under various conditions, even if a pressure sensor is provided on each wheel and an accurate wheel cylinder pressure (braking fluid pressure) is obtained, the braking fluid pressure (that is, the friction member) is obtained. The braking force calculated from (the pressing force) includes an error. An object of the present invention is to provide a wheel braking force estimation device that can appropriately estimate the braking force of each wheel even if the friction coefficient of the friction member varies. Another object of the present invention is to provide a vehicle motion control device that stabilizes the motion of a vehicle by performing at least one of braking control and steering control based on the braking force estimated by the device.

  The wheel braking force estimation device is a pressing amount (Pwa [) of a friction member (PD [**]) of a braking means that generates a braking force (Fxa [**]) on each wheel (WH [**]) of a vehicle. **]) is applied to the vehicle based on the pressing amount acquisition means (PWA), the longitudinal acceleration acquisition means (GXA) that acquires the longitudinal acceleration (Gxa) of the vehicle, and the longitudinal acceleration (Gxa). An estimation means (FXE) for calculating a deceleration force (Fgx) and estimating the braking force (Fxa [**]) based on the deceleration force (Fgx) and the pressing amount (Pwa [**]); Is provided.

  The estimation means (FXE) is configured such that a ratio (Pwa [**] / ΣPwa [*) of the pressing amount of one wheel of the vehicle to a total sum (ΣPwa [**]) of the pressing amount of all the wheels of the vehicle. It is desirable to estimate the braking force (Fxa [**]) by multiplying the deceleration force (Fgx) by *]).

  The wheel braking force estimation device includes travel resistance acquisition means (GRR) for acquiring travel resistance (Grr) acting on the vehicle, and the estimation means (FXE) is configured to calculate the travel resistance (Gxa) from the longitudinal acceleration (Gxa). The deceleration force (Fgx) can be calculated excluding Grr). The wheel braking force estimation device includes vehicle speed acquisition means (VXA) for acquiring the travel speed (Vxa) of the vehicle, and the travel resistance acquisition means (GRR) is based on the travel speed (Vxa). (Grr) may be calculated. The wheel braking force estimation device further includes steering angle acquisition means (SAA) for acquiring the steering angle (Saa) of the vehicle, and lateral acceleration acquisition means (GYA) for acquiring the lateral acceleration (Gya) of the vehicle. The travel resistance acquisition means (GRR) can calculate the travel resistance (Grr) based on the steering angle (Saa) and the lateral acceleration (Gya).

  The wheel braking force estimation device acquires a ground load acquisition means (FZA) for acquiring a ground load (Fza [**]) of each wheel of the vehicle and a friction coefficient (μmax) of a road surface on which the vehicle travels. Friction coefficient acquisition means (MMX), the estimation means (FXE) is based on the contact load (Fza [**]) and the friction coefficient (μmax) of the road surface, the braking force (Fxa [* *]) Can be restricted (upper limit).

In a vehicle motion control device that stabilizes the motion of a running vehicle, a friction member (PD [*] of a braking unit that generates a braking force (Fxa [**]) on each wheel (WH [**]). *]) weight pressing the (Pwa [**]) pressing amount acquisition means for acquiring (PWA), said front and rear acceleration acquisition means for acquiring a longitudinal acceleration (Gxa) of the vehicle (GXA), before Symbol longitudinal acceleration ( A deceleration force (Fgx) acting on the vehicle is calculated based on Gxa), and the braking force (Fxa [**]) is calculated based on the deceleration force (Fgx) and the pressing amount (Pwa [**]). ) To estimate the braking force (Fxe [**]), and based on the estimated braking force (Fxe [**]), the vehicle is subjected to braking control and steering control. control means for stabilizing the movement of the vehicle by performing at least one (CTL) before and Ru with a Symbol estimating means (F E) is a ratio (Pwa [**] / ΣPwa [**]) of the pressing amount of one wheel of the vehicle to the total pressing force (ΣPwa [**]) of all the wheels of the vehicle. , you calculating the estimated braking force by multiplying the deceleration force (Fgx) (Fxe [**] ).

  In the wheel braking force estimation device, a deceleration force (total braking force of all wheels) acting on the vehicle is calculated based on a signal from the longitudinal acceleration acquisition means (longitudinal acceleration sensor), and based on this, the braking force of each wheel is calculated. Therefore, even if the friction coefficient (μpad) of the friction member (for example, the brake pad) of the friction brake device fluctuates, the braking force of each wheel can be estimated appropriately. Each wheel brake condition (for example, the temperature of the friction member and the viscosity of the brake fluid) is considered to be substantially the same, so by distributing the deceleration force to each wheel at the ratio of the pressing amount of each wheel, the accuracy of each wheel is improved. The braking force can be estimated.

  The signal of the longitudinal acceleration acquisition means (for example, the longitudinal acceleration sensor fixed to the vehicle body) includes a component due to running resistance (rolling resistance, air resistance, cornering resistance, etc.). In the wheel braking force estimation device, the running resistance component included in the signal of the longitudinal acceleration acquisition means is estimated by the running resistance acquisition means, and this is compensated, so that the braking force of each wheel can be estimated with high accuracy.

  When the front / rear slip is within a predetermined range (the so-called μ-S characteristic is a range less than or equal to the μ peak value), braking torque (that is, the pressing force of the friction member) applied to the wheel (pneumatic tire) is generated. There is a linear relationship with the braking force. However, when the front / rear slip is excessive, the braking force decreases as the pressing amount of the friction member (for example, braking fluid pressure) increases. In the wheel braking force estimation device, the maximum braking force (= μmax · Fza [*] that can generate the braking force of each wheel based on the ground contact load (Fza [**]) and the road surface friction coefficient (μmax). *]) (The maximum braking force is set as the upper limit value), the braking force can be properly estimated even when the front and rear slip is excessive.

  In a vehicle motion control apparatus that estimates the braking force of each wheel and executes vehicle stabilization control (braking control, steering control) based on this braking force, each wheel even if the friction coefficient of the friction member fluctuates. Since the braking force can be accurately estimated, the vehicle stabilization control can be appropriately executed. Similar to the above, the braking force of each wheel is accurately estimated by allocating the deceleration force to each wheel at the ratio of the pressing amount (for example, braking fluid pressure) of each wheel, and the vehicle stabilization control is appropriately executed. Can be done.

1 is a diagram illustrating an overall configuration of a vehicle including a wheel braking force estimation device according to an embodiment of the present invention and a vehicle motion control device including the device. It is a functional block diagram for demonstrating the braking force estimation apparatus of the wheel which concerns on embodiment of this invention. It is a functional block diagram for demonstrating the calculation process of the correction acceleration in FIG. It is a figure for demonstrating the map (characteristic) which calculates the 1st driving | running | working resistance value in FIG. It is a functional block diagram for demonstrating the calculation process of the 2nd running resistance value in FIG. It is another functional block diagram for demonstrating the calculation process of the 2nd driving | running | working resistance value in FIG. FIG. 3 is a functional block diagram for calculating an estimated braking force in FIG. 2 with a limit. It is a functional block diagram for demonstrating the vehicle motion control apparatus based on the estimated braking force estimated by the braking force estimation apparatus of the wheel which concerns on embodiment of this invention. It is a functional block diagram for demonstrating the braking control calculation block in FIG. It is a functional block diagram for demonstrating the steering control calculation block in FIG.

  FIG. 1 is a diagram illustrating an overall configuration of a vehicle including a wheel braking force estimation device according to an embodiment of the present invention and a vehicle motion control device using the device.

  The subscript [**] attached to the end of various symbols indicates whether the various symbols are related to any of the four wheels. “F” indicates a front wheel, “r” indicates a rear wheel, “m” indicates a right wheel with respect to the traveling direction of the vehicle, and “h” indicates a left wheel. Therefore, “fh” indicates the left front wheel, “fm” indicates the right front wheel, “rh” indicates the left rear wheel, and “rm” indicates the right rear wheel. The acceleration / deceleration of the vehicle is generally given a positive / negative sign, for example, acceleration is expressed as a positive sign and deceleration is expressed as a negative sign. However, when describing the magnitude relationship of the values or the increase / decrease in the values, it becomes very complicated when the sign is taken into account. Therefore, in the description, unless there is a particular limitation, the absolute value magnitude relationship and the absolute value increase / decrease are represented. The predetermined value is a positive value.

  The vehicle includes a wheel speed sensor WS [**] that detects the wheel speed Vwa [**], and a rotation angle θsw of the steering wheel SW (from a neutral position “0” of the steering device that corresponds to the vehicle traveling straight). Steering wheel angle sensor SA for detecting the steering wheel, front wheel steering angle sensor SB for detecting the steering angle δfa of the steered wheel (front wheel), and steering torque sensor ST for detecting the torque Tsw when the driver operates the steering wheel SW A yaw rate sensor YR that detects an actual yaw rate Yra acting on the vehicle, a longitudinal acceleration sensor GX that detects a longitudinal acceleration Gxa in the longitudinal direction of the vehicle body, a lateral acceleration sensor GY that detects a lateral acceleration Gya in the lateral direction of the vehicle body, A pressing amount sensor (for example, a hoisting amount sensor) that detects a pressing amount (for example, a brake fluid pressure of the wheel cylinder WC [**]) Pwa [**], which will be described later. And Rushirinda pressure sensor) PW [**], an engine rotational speed sensor NE for detecting a rotational speed Nea engine EG, throttle position sensor TS is provided for detecting the opening Tsa of the throttle valve of the engine.

  As means for detecting the driver's driving operation, an acceleration operation amount sensor AS for detecting the operation amount Asa of the driver's acceleration operation member (for example, accelerator pedal) AP, and the driver's braking operation member (for example, brake) Pedal) A braking operation amount sensor BS for detecting the operation amount Bsa of the BP and a shift position sensor HS for detecting the shift position Hsa of the speed change operation member SF are provided.

  The vehicle also includes a brake actuator BRK that controls the brake fluid pressure, a throttle actuator TH that controls the throttle valve, a fuel injection actuator FI that controls fuel injection, and an automatic transmission AT that controls the shift. It has been.

  In addition, the vehicle includes an electronic control unit ECU that is electrically connected to the above-described various actuators (such as BRK) and the above-described various sensors (such as WS [**]). The electronic control unit ECU is a microcomputer composed of a plurality of independent electronic control units ECU (ECUb, ECUs, ECUe, ECUa) connected to each other via a communication bus CB. Each system electronic control unit (ECUb, etc.) in the electronic control unit ECU executes a dedicated control program. Signals (sensor values) of various sensors and signals (internally calculated values) calculated in each electronic control unit (ECUb or the like) are shared via the communication bus CB.

  This apparatus is provided in the electronic control unit ECU. For example, it is provided in the brake system electronic control unit ECUb that controls the brake actuator BRK. In the present apparatus, the corrected longitudinal acceleration Gxs (longitudinal acceleration excluding the influence of running resistance) is calculated based on the actual longitudinal acceleration Gxa detected by the longitudinal acceleration sensor GX, the vehicle speed Vxa, and the like. Here, the longitudinal acceleration Gxa can be calculated by differentiating the vehicle speed Vxa. Further, based on the corrected longitudinal acceleration Gxs, vehicle specifications (weight, center of gravity position, inertial mass, etc.) that vary depending on the loading state of the vehicle are estimated.

  In the brake system electronic control unit ECUb, slip such as anti-skid control (ABS control), traction control (TCS control), etc. based on signals from the wheel speed sensor WS [**], the yaw rate sensor YR, the lateral acceleration sensor GY, etc. Suppression control (longitudinal force control) is executed. Further, based on the wheel speed Vwa [**] of each wheel detected by the wheel speed sensor WS [**], the traveling speed Vxa of the vehicle is calculated by a known method.

  In the steering system electronic control unit ECUs, electric power steering control (EPS control) is executed based on a signal from the steering torque sensor ST or the like. Further, variable steering gear ratio control (VGR control) is executed based on the vehicle speed Vxa calculated by the brake system electronic control unit ECUb.

  In the engine system electronic control unit ECUe, the throttle actuator TH and the fuel injection actuator FI are controlled based on the signal Asa from the acceleration operation amount sensor AS and the like. In the transmission system electronic control unit ECUa, control of the gear ratio of the automatic transmission AT is executed.

  The brake actuator BRK has a known configuration including a plurality of electromagnetic valves (hydraulic pressure regulating valves), a hydraulic pump, an electric motor, and the like. When the brake control is not executed, the brake actuator BRK supplies the brake fluid pressure corresponding to the operation of the brake operation member BP by the driver to the wheel cylinder WC [**] of each wheel, and brakes each wheel. A braking torque corresponding to the operation of the operation member (brake pedal) BP is applied. When executing brake control such as anti-skid control (ABS control), traction control (TCS control), or vehicle stability control (ESC control) that suppresses vehicle understeer and oversteer, the brake actuator BRK controls the brake pedal BP. Independent of the operation, the brake fluid pressure for each wheel cylinder WC [**] is controlled, and the brake torque can be adjusted for each wheel.

  Each wheel is provided with a well-known wheel cylinder WC [**], brake caliper BC [**], brake pad PD [**], and brake rotor RT [**] as braking means. When brake fluid pressure is applied to the wheel cylinder WC [**] provided in the brake caliper BC [**], the brake pad PD [**] is pressed against the brake rotor RT [**], and the friction force Thus, a braking torque is applied to each wheel. Note that the control of the braking torque is not limited to that based on the braking hydraulic pressure, and can be performed using an electric brake device.

  In the front wheel steering control mechanism STR, the steering wheel SW operated by the driver is connected to the electric power steering mechanism EPS via the upper steering shaft USS, the steering gear ratio variable mechanism VGR, and the lower steering shaft LSS. Thereby, the rotation of the steering wheel SW is transmitted to the EPS.

  The electric power steering mechanism EPS is configured by one of known configurations including an electric motor, a rack & pinion, and the like. An electric motor (not shown) converts the rotational motion of the lower steering shaft LSS into a translational motion of the rod RD in the left-right direction of the vehicle body and drives the rod RD in a direction to assist the rotational torque received from the lower steering shaft LSS. It is supposed to be generated by. As described above, when the steering wheel SW is rotated by the driver, the front wheels WH [fm] and WH [fh] that are steered wheels are steered while the steering torque of the driver is assisted by the assist force. It has become.

  The steering gear ratio variable mechanism VGR is configured by one of known configurations including an electric motor, a speed reducer, and the like. By controlling the rotation angle of the electric motor (not shown), the steering angle of the front wheels (steering wheels) WH [fm], WH [fh] can be controlled independently of the rotation angle of the steering wheel. Yes. In the variable steering gear ratio control, the ratio of the rotation angle of the steering wheel SW to the steering angle of the front wheels WH [fm] and WH [fh] (steering gear ratio) can be changed.

  FIG. 2 is a diagram for explaining the embodiment of the present invention, and is a functional block diagram for calculating an estimated braking force Fxe [**]. These arithmetic processes are programmed in the electronic control unit ECU (for example, in the brake system electronic control unit ECUb).

  In each wheel pressing amount acquisition calculation block PWA, the pressing amount Pwa [**] of each wheel is calculated. The pressing amount Pwa [**] is a value corresponding to the force (pressing force) by which the brake pad PD [**] is pressed against the brake rotor RT [**], for example, within the wheel cylinder WC [**]. Braking fluid pressure. The pressing amount Pwa [**] is calculated based on the detection signal of PW [**]. Alternatively, the pressing amount Pwa [**] can be estimated based on the operating states of the plurality of electromagnetic valves of the brake actuator BRK.

  In the pressing amount total calculation block PWS, the pressing amount total Pws is calculated based on the pressing amount Pwa [**]. The total pressing amount Pws is a total sum of the pressing amounts Pwa [**] of each wheel and is calculated by Pws = ΣPwa [**].

  In the pressing amount ratio calculation block HPW, the pressing amount ratio Hpw [**] is calculated based on the pressing amount Pwa [**] and the total pressing amount Pws. The pressing amount ratio Hpw [**] is a ratio of the pressing amount Pwa [**] of each wheel to the total pressing amount Pws, and is calculated by Hpw [**] = Pwa [**] / Pws.

  In the longitudinal acceleration acquisition calculation block GXA, the longitudinal acceleration Gxa is acquired. The longitudinal acceleration Gxa is calculated based on a signal detected by the longitudinal acceleration sensor GX. Further, the longitudinal acceleration Gxa can be calculated by differentiating the vehicle traveling speed (vehicle speed) Vxa calculated based on the wheel speed Vwa [**] detected by the wheel speed sensor WS [**].

  A vehicle deceleration force calculation block FGX calculates a vehicle deceleration force Fgx based on the longitudinal acceleration Gxa. The vehicle deceleration force Fgx is a force that decelerates the vehicle, and is a total sum of braking forces generated by the wheels, and is calculated by Fgx = Mvh · Gxa. Here, Mvh is a vehicle weight (predetermined value). Instead of the longitudinal acceleration Gxa, a value (corrected acceleration) Gxs obtained by removing a running resistance (wheel rolling resistance or the like) from the longitudinal acceleration Gxa can be used. A method for calculating the corrected acceleration Gxs will be described later.

  In each wheel braking force estimation calculation block FXE, an estimated braking force Fxe [**] of each wheel is calculated based on the deceleration force Fgx and the pressing amount ratio Hpw [**]. The estimated braking force Fxe [**] is calculated by Fxe [**] = Hpw [**] · Fgx.

  A deceleration force (longitudinal force for decelerating the vehicle) Fgx corresponding to the longitudinal acceleration Gxa is distributed to each wheel based on the pressing amount ratio Hpw [**] of each wheel, and an estimated braking force Fxe [**] is obtained. Calculated. Since the braking force of each wheel is a value corresponding to the friction coefficient μpad (specifically, μpad · Pwa [**]) of the brake pad PD [**], the braking force changes due to the variation of the friction coefficient μpad. To do. If there is a difference between the actual value of the brake pad friction coefficient μpad and the value used for calculating the estimated braking force Fxe [**] (a predetermined value set in advance in the calculation process), the estimated braking force Fxe [* *] Error increases. Since the braking force (deceleration force Fgx) acting on the entire vehicle is calculated based on the longitudinal acceleration Gxa, the above-described increase in error can be suppressed.

  Further, in the estimation calculation of the brake fluid pressure based on the operation state of the solenoid valve (that is, the calculation for estimating the pressing amount Pwa [**] from the operation state of the BRK solenoid valve), the braking to the wheel cylinder WC [**] is performed. The fluid pressure is calculated by estimating the amount of fluid movement (that is, the volume of braking fluid that moves to the wheel cylinder WC [**]). The brake fluid pressure estimation is affected by the temperature of the brake fluid (specifically, the viscosity of the brake fluid depending on the temperature). Furthermore, since the amount of movement of the brake fluid is obtained by integration calculation, it is affected by the timing of starting the calculation (specifically, the length of the integration calculation time). The absolute value of the estimated pressing amount Pwa [**] includes errors such as the above-described viscosity and integration time. However, since the pressing amount ratio Hpw [**], which is a relative amount with respect to the pressing amount total Pws, is used in the calculation of the estimated braking force Fxe [**], the influence of these errors can be compensated.

  FIG. 4 is a functional block diagram of a calculation process of a corrected acceleration Gxs obtained by correcting the longitudinal acceleration Gxa based on running resistance using FIG. 3. Here, the corrected acceleration Gxs is the longitudinal acceleration generated by the longitudinal force generated by the wheel, and is a value in which the longitudinal acceleration component caused by the running resistance is compensated. These arithmetic processes are programmed in the electronic control unit ECU (for example, in the brake system electronic control unit ECUb).

  In the longitudinal acceleration acquisition calculation block GXA, the longitudinal acceleration Gxa is acquired. The longitudinal acceleration Gxa is calculated based on a signal detected by the longitudinal acceleration sensor GX. Further, the longitudinal acceleration Gxa can be calculated by differentiating the vehicle speed Vxa calculated based on the wheel speed Vwa [**] detected by the wheel speed sensor WS [**].

  Lateral acceleration Gya is calculated in the lateral acceleration acquisition calculation block GYA. The lateral acceleration Gya is calculated based on a signal detected by the lateral acceleration sensor GY. Moreover, it can be calculated based on the yaw rate Yra detected by the yaw rate sensor YR.

  In the steering angle acquisition calculation block SAA, the steering angle Saa is calculated. The steering angle Saa is calculated based on a signal (steering wheel angle θsw that is the rotation angle of the steering wheel SW) detected by the steering wheel angle sensor SA. Further, it can be calculated based on the front wheel steering angle δfa detected by the front wheel steering angle sensor FS. That is, the steering angle Saa can be calculated based on at least one of the steering wheel angle θsw and the front wheel steering angle δfa.

  The vehicle speed Vxa is calculated in the vehicle speed acquisition calculation block VXA. The vehicle speed Vxa is calculated based on the wheel speed Vwa [**] detected by the wheel speed sensor WS [**].

  The running resistance acquisition means GRR calculates running resistance values Grk, Grc, and Grr representing running resistances such as wheel rolling resistance, body air resistance, and wheel cornering resistance. The travel resistance acquisition means GRR is configured by a first travel resistance calculation block GRK, a second travel resistance calculation block GRC, and an addition means CXS.

  In the first running resistance calculation block GRK, the first running resistance value Grk is calculated. The first running resistance value Grk is a component due to the rolling resistance of the wheels included in the longitudinal acceleration Gxa and the air resistance of the vehicle body. The rolling resistance includes not only the rolling resistance of the wheel (pneumatic tire) itself but also the frictional resistance of the axle and the dragging resistance of the friction brake. The first running resistance value Grk is calculated based on the calculation map (characteristic) shown in FIG. 4 based on the vehicle speed Vxa. The first running resistance value Grk is calculated as a predetermined value gk1 when the vehicle speed Vxa is extremely low, and increases as the vehicle speed Vxa increases.

  In the second running resistance calculation block GRC, the second running resistance value Grc is calculated. The second running resistance value Grc is a component corresponding to the vehicle longitudinal direction of the lateral force generated by the wheels included in the longitudinal acceleration Gxa. The calculation of the second running resistance value Grc will be described later.

  In the adding means CXS, the first traveling resistance value Grk and the second traveling resistance value Grc are added to calculate the adjusted traveling resistance value Grr. The adjusted travel resistance value Grr is a value for calculating the corrected acceleration Gxs by adjusting the longitudinal acceleration Gxa detected by the longitudinal acceleration sensor GX or the like. Then, in the corrected acceleration calculation block GXS, the adjusted travel resistance value Grr is removed (subtracted) from the longitudinal acceleration Gxa to calculate the corrected acceleration Gxs. That is, the corrected acceleration (corrected longitudinal acceleration) Gxs is a value obtained by removing the running resistance component from the signals from the longitudinal acceleration sensor GX and the like, and is the longitudinal acceleration generated in the vehicle only by the longitudinal force of the wheels.

  Any one of the first running resistance calculation block GRK and the second running resistance calculation block GRC may be omitted. When the first running resistance calculation block GRK is omitted, the second running resistance value Grc is set as the adjusted running resistance value Grr as it is. When the second running resistance calculation block GRC is omitted, the first running resistance value Grk is set as the adjusted running resistance value Grr as it is.

  The signal of the longitudinal acceleration acquisition means (for example, the longitudinal acceleration sensor GX fixed to the vehicle body) includes components due to running resistance such as rolling resistance of the wheel, air resistance of the vehicle body, cornering resistance of the wheel, etc., but correction means GRR Since the running resistance component is removed based on the running resistance values (Grc, Grk, Grr) calculated by (GRC, GRK, CXS), the longitudinal acceleration generated only by the longitudinal force (braking / driving force) of the wheels Can be obtained with high accuracy.

  FIG. 5 is a functional block diagram for explaining the calculation of the second running resistance value Grc in the second running resistance calculation block GRC of FIG.

  In the vehicle body slip angle calculation block BTA, the vehicle body slip angle βa is calculated based on the yaw rate Yra, the vehicle speed Vxa, the steering angle Saa, the lateral acceleration Gya, and a known calculation method. For example, a vehicle body slip angular velocity dβ is calculated, and a value obtained by integrating dβ (= ∫ (Yra−Gya / Vxa) dt) and a value calculated based on the steering angle Saa, the vehicle speed Vxa, and the vehicle model. Based on this, βa can be calculated.

  In the front and rear wheel slip angle calculation block ALF, the front wheel slip angle αfa and the rear wheel slip angle αra are calculated based on the vehicle body slip angle βa and the steering angle Saa. For example, the front wheel slip angle αfa can be calculated by αfa = βa + Saa, and the rear wheel slip angle αra can be calculated by αra = βa.

  In the lateral acceleration front and rear wheel component calculation block GFR, the front wheel component (lateral acceleration generated by the front wheel) Gyf and the rear wheel component (lateral acceleration generated by the rear wheel) Gyr of the lateral acceleration are calculated. For example, the front wheel component Gyf of the lateral acceleration can be calculated by Gyf = Gy · Lr / L, and the rear wheel component Gyr of the lateral acceleration can be calculated by Gyr = Gy · Lf / L. Here, L is the wheel base, Lf is the distance from the center of gravity to the front wheel axis, and Lr is the distance from the center of gravity to the rear wheel axis.

  In the longitudinal component calculation block GYM, the second running resistance value Grc is calculated based on the longitudinal acceleration front and rear wheel components Gyf and Gyr and the front and rear wheel slip angles αfa and αra. For example, it can be calculated based on Grc = Gyf · sin (αfa) + Gyr · sin (αra).

  FIG. 6 is another functional block diagram for explaining the calculation of the second traveling resistance value Grc in the second traveling resistance calculation block GRC of FIG. Since the cornering resistance is approximately a value corresponding to the turning state, the second traveling resistance value Grc can be calculated based on the lateral acceleration Gya and the steering angle Saa using a preset characteristic (calculation map). The second running resistance value Grc is calculated so as to increase as at least one of the lateral acceleration Gya and the steering angle Saa increases.

  FIG. 7 is a diagram for explaining another embodiment of the present invention, and is a functional block diagram for calculating with an estimated braking force Fxe [**] limited (upper limit). Although the longitudinal force (braking / driving force) is generated by the longitudinal slip of the wheel, the longitudinal force has a peak value at a predetermined longitudinal slip (for example, the slip ratio is about 15%). This peak value is affected by the ground load (vertical load) and the road surface friction coefficient.

  In each wheel contact load acquisition calculation block FZA, the contact load Fza [**] of each wheel is calculated. The ground load Fza [**] is calculated based on an output signal of a load sensor (not shown) provided in each wheel. Further, load fluctuation (static load (preliminary load) in advance) is based on at least one of the outputs (longitudinal acceleration Gxa and lateral acceleration Gya) of the longitudinal acceleration sensor GX and lateral acceleration sensor GY and a known method. The ground load Fza [**] can be determined by calculating the fluctuation amount) from the set predetermined value). In the road surface friction coefficient acquisition calculation block MMX, a friction coefficient (road surface friction coefficient) μmax between the wheel and the road surface is calculated. The road surface friction coefficient μmax is calculated based on at least one of the longitudinal acceleration Gxa and the lateral acceleration Gya and a known method.

  In the limit calculation block LMT, the estimated braking force Fxe [**] is restricted based on the ground contact load Fza [**] and the road surface friction coefficient μmax, and the estimated braking force Fxe [**] after the restriction is given. Is calculated. Specifically, the estimated braking force Fxe [**] calculated in each wheel braking force estimation calculation block FXE is compared with μmax · Fza [**], and the larger value is the estimated braking force after the restriction. Calculated as Fxe [**]. Since the estimated braking force Fxe [**] is limited to the peak value (upper limit value) of the longitudinal force calculated based on the ground contact load Fza [**] and the road surface friction coefficient μmax, the estimated braking force Fxe [** The calculation accuracy can be improved.

  Next, using FIG. 8 which is a functional block diagram, at least one of braking control and steering control based on the estimated braking force Fxe [**] estimated by the wheel braking force estimation device. A vehicle motion control apparatus that executes the above will be described.

  The control means CTL calculates a target value for controlling at least one of the brake actuator BRK, the electric power steering mechanism EPS, and the steering gear ratio variable mechanism VGR based on the estimated braking force Fxe [**]. The The control means CTL includes a braking control calculation block BFC for individually controlling the braking force of each wheel, a steering torque applied to the steering wheel SW, and a steering wheel steering angle (front wheel steering angle). A steering control calculation block STC for controlling at least one of them is included. Any one of the braking control calculation block BFC and the steering control calculation block STC may be omitted.

  The braking control calculation block BFC will be described with reference to the functional block diagram of FIG.

  In the braking control target value calculation block FXT, control in vehicle stabilization control for stabilizing the vehicle based on the steering angle Saa (steering wheel angle θsw, front wheel steering angle δfa), vehicle speed Vxa, and turning state amount Taa. The power target value Fxt [**] is calculated. Here, the turning state amount Taa is a state amount representing the turning motion of the vehicle such as the yaw rate Yra and the lateral acceleration Gya. If it is determined based on the steering angle Saa, the vehicle speed Vxa, and the turning state amount Taa that the steering characteristic of the vehicle is excessive oversteer, at least the braking force target value Fxt [**] of the vehicle's turning outer front wheel. Is increased. Further, if it is determined that the steering characteristic of the vehicle is excessive understeer based on the steering angle Saa, the vehicle speed Vxa, and the turning state amount Taa, at least the braking force target value Fxt [ **] is increased. Then, the brake actuator BRK is controlled based on the braking force target value Fxt [**] calculated by the braking control target value calculation block FXT.

  The actual lateral force value calculation block FYA calculates the actual lateral force value Fya [**] of each wheel based on the estimated braking force Fxe [**] and the turning state amount Taa. Specifically, using the balance formula of the force in the vehicle lateral direction and the center of gravity, the lateral acceleration Gya, the yaw angular acceleration dYr obtained by differentiating the yaw rate Yra, and the estimated braking force Fxe [**] The lateral force actual value Fya [**] is calculated based on the braking force difference ΔFx.

  In the lateral force reference value calculation block FYK, the lateral force reference value Fyk [**] is calculated based on the steering angle Saa and the vehicle speed Vxa. The lateral force reference value Fyk [**] is a target value of the wheel lateral force required for the turning motion of the vehicle when the steering operation of the steering angle Saa is performed at the vehicle speed Vxa. In the calculation of the lateral force reference value Fyk [**], the road surface friction coefficient μmax can be considered.

  The comparison means DFY compares the lateral force actual value Fya [**] with the lateral force reference value Fyk [**], and the comparison result (lateral force deviation) ΔFy [**] (= Fya [**] -Fyk [**]) is output. In the braking control target value calculation block FXT, the braking force target value Fxt [**] is adjusted based on the lateral force deviation ΔFy [**]. Specifically, the increase in the braking force target value Fxt [**] is limited when the lateral force deviation ΔFy [**] is equal to or less than a predetermined value dfy1. That is, when the actual lateral force of the wheel is reduced, the degree of increase in the braking force target value Fxt [**] is reduced, and the necessary lateral force can be ensured.

  Instead of the lateral force deviation ΔFy [**] of each wheel, the lateral force deviation ΔFy [#] on the axle can be used. Here, the subscript [#] indicates that it relates to either the front wheel shaft or the rear wheel shaft, [f] indicates the front wheel shaft, and [r] indicates the rear wheel shaft. The lateral force deviation ΔFy [#] is a lateral acceleration Gya, a yaw angular acceleration dYr obtained by differentiating the yaw rate Yra, and an estimated braking force Fxe [**] using a balance formula of forces in the lateral direction of the vehicle and around the center of gravity. The lateral force actual value Fya [#] for each axle is calculated based on the left-right braking force difference ΔFx obtained from

  The steering control calculation block STC will be described with reference to the functional block diagram of FIG.

  The braking force left / right difference calculation block DFX calculates the braking force left / right difference ΔFx based on the estimated braking force Fxe [**]. The left-right braking force difference ΔFx is calculated when the vehicle travels on a μ-split road surface (a road surface having a different friction coefficient between the left and right wheels) and ABS control (control to prevent wheel lock based on wheel speed) is executed. Can be broken.

  In the steering torque target value calculation block TST, the steering torque target value Tst is calculated based on the left / right braking force difference ΔFx. Specifically, the steering torque target value Tst is such that the steering wheel SW is moved in the steering direction to suppress vehicle deflection (yawing motion) generated by the braking force difference when the left-right braking force difference ΔFx is equal to or greater than a predetermined value dfx1. The steering torque target value Tst is calculated. Then, the electric power steering mechanism EPS is controlled based on the steering torque target value Tst.

  In the steering angle target value calculation block VGT, the steering angle target value Vgt is calculated based on the left / right braking force difference ΔFx. Specifically, the steering angle target value Vgt is determined by the steering wheel (front wheel) in the steering direction that suppresses vehicle deflection (yawing motion) generated by the braking force difference when the left-right braking force difference ΔFx is equal to or greater than a predetermined value dfx2. A steering angle target value Vgt is calculated so as to be steered. Then, the steering gear ratio variable mechanism VGR is controlled based on the steering angle target value Vgt.

  When ABS control is executed while traveling on a μ-split road surface, the vehicle is deflected in a direction with a higher road surface friction coefficient. Steering control prompts the driver to perform a counter steer operation (a steering operation that suppresses vehicle deflection) by applying steering torque, and automatically executes the counter steer by adjusting the steering angle of the steered wheels. Furthermore, since the steering control is executed based on the left / right braking force difference ΔFx calculated based on the longitudinal acceleration (corrected acceleration) Gxs from which the running resistance has been removed, highly accurate steering control can be performed. Note that one of the steering torque target value calculation block TST and the steering angle target value calculation block VGT may be omitted.

ECU ... Electronic control unit, GX ... Longitudinal acceleration sensor, GY ... Lateral acceleration sensor, WS [**] ... Wheel speed sensor, YR ... Yaw rate sensor, PW [**] ... Push amount sensor, SW ... Steering wheel, SA ... Steering wheel angle sensor, FS ... Front wheel steering angle sensor, PD [**] ... Friction member, BRK ... Brake actuator, EPS ... Electric power steering mechanism, VGR ... Steering gear ratio variable mechanism

Claims (6)

A pressing amount acquisition means for acquiring a pressing amount of a friction member of a braking means for generating a braking force on each wheel of the vehicle;
Longitudinal acceleration acquisition means for acquiring longitudinal acceleration of the vehicle;
An estimation means for calculating a deceleration force acting on the vehicle based on the longitudinal acceleration and estimating the braking force based on the deceleration force and the pressing amount;
In the braking force estimating device for vehicle wheels provided with,
The estimation means estimates the braking force by multiplying the deceleration force by a ratio of the pressing amount of one wheel of the vehicle to the sum of the pressing amounts of all the wheels of the vehicle. Wheel braking force estimation device. A wheel braking force estimation device according to claim 1 ,
A running resistance obtaining means for obtaining running resistance acting on the vehicle;
The wheel braking force estimation device according to claim 1, wherein the estimating means calculates the deceleration force by removing the running resistance from the longitudinal acceleration. A wheel braking force estimation device according to claim 2 ,
Vehicle speed acquisition means for acquiring the traveling speed of the vehicle,
The wheel braking force estimation device according to claim 1, wherein the running resistance acquisition means calculates the running resistance based on the running speed. A wheel braking force estimation device according to claim 2 or claim 3 ,
Steering angle acquisition means for acquiring the steering angle of the vehicle;
Lateral acceleration acquisition means for acquiring the lateral acceleration of the vehicle,
The wheel running force obtaining device calculates the running force based on the steering angle and the lateral acceleration, and the braking force estimating device for a wheel according to claim 1, wherein: A wheel braking force estimation device according to any one of claims 1 to 4 ,
A contact load acquisition means for acquiring a contact load of each wheel of the vehicle;
Friction coefficient obtaining means for obtaining a friction coefficient of a road surface on which the vehicle travels,
The wheel braking force estimation device according to claim 1, wherein the estimating means limits the braking force based on the ground load and a friction coefficient of the road surface. In a vehicle motion control device that stabilizes the motion of a running vehicle,
A pressing amount acquisition means for acquiring a pressing amount of the friction member of the braking means for generating a braking force on each wheel;
Longitudinal acceleration acquisition means for acquiring longitudinal acceleration of the vehicle ;
Calculating a deceleration force acting on the vehicle based on the previous SL longitudinal acceleration, an estimation unit reducer speed, and that the braking force is estimated based on the pressing amount, the estimated braking force,
Control means for stabilizing the movement of the vehicle by executing at least one of braking control and steering control on the vehicle based on the estimated braking force;
A vehicles motion control device provided with,
The estimation means calculates the estimated braking force by multiplying the deceleration force by a ratio of the pressing amount of one wheel of the vehicle to the sum of the pressing amounts of all the wheels of the vehicle. A vehicle motion control device.

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